| Step | Hyp | Ref | Expression | 
|---|
| 1 |  | cofuval.b | . . . . 5
⊢ 𝐵 = (Base‘𝐶) | 
| 2 |  | cofuval.f | . . . . 5
⊢ (𝜑 → 𝐹 ∈ (𝐶 Func 𝐷)) | 
| 3 |  | cofuval.g | . . . . 5
⊢ (𝜑 → 𝐺 ∈ (𝐷 Func 𝐸)) | 
| 4 | 1, 2, 3 | cofuval 17928 | . . . 4
⊢ (𝜑 → (𝐺 ∘func 𝐹) = 〈((1st
‘𝐺) ∘
(1st ‘𝐹)),
(𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ ((((1st ‘𝐹)‘𝑥)(2nd ‘𝐺)((1st ‘𝐹)‘𝑦)) ∘ (𝑥(2nd ‘𝐹)𝑦)))〉) | 
| 5 | 4 | fveq2d 6909 | . . 3
⊢ (𝜑 → (2nd
‘(𝐺
∘func 𝐹)) = (2nd
‘〈((1st ‘𝐺) ∘ (1st ‘𝐹)), (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ ((((1st ‘𝐹)‘𝑥)(2nd ‘𝐺)((1st ‘𝐹)‘𝑦)) ∘ (𝑥(2nd ‘𝐹)𝑦)))〉)) | 
| 6 |  | fvex 6918 | . . . . 5
⊢
(1st ‘𝐺) ∈ V | 
| 7 |  | fvex 6918 | . . . . 5
⊢
(1st ‘𝐹) ∈ V | 
| 8 | 6, 7 | coex 7953 | . . . 4
⊢
((1st ‘𝐺) ∘ (1st ‘𝐹)) ∈ V | 
| 9 | 1 | fvexi 6919 | . . . . 5
⊢ 𝐵 ∈ V | 
| 10 | 9, 9 | mpoex 8105 | . . . 4
⊢ (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ ((((1st ‘𝐹)‘𝑥)(2nd ‘𝐺)((1st ‘𝐹)‘𝑦)) ∘ (𝑥(2nd ‘𝐹)𝑦))) ∈ V | 
| 11 | 8, 10 | op2nd 8024 | . . 3
⊢
(2nd ‘〈((1st ‘𝐺) ∘ (1st ‘𝐹)), (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ ((((1st ‘𝐹)‘𝑥)(2nd ‘𝐺)((1st ‘𝐹)‘𝑦)) ∘ (𝑥(2nd ‘𝐹)𝑦)))〉) = (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ ((((1st ‘𝐹)‘𝑥)(2nd ‘𝐺)((1st ‘𝐹)‘𝑦)) ∘ (𝑥(2nd ‘𝐹)𝑦))) | 
| 12 | 5, 11 | eqtrdi 2792 | . 2
⊢ (𝜑 → (2nd
‘(𝐺
∘func 𝐹)) = (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ ((((1st ‘𝐹)‘𝑥)(2nd ‘𝐺)((1st ‘𝐹)‘𝑦)) ∘ (𝑥(2nd ‘𝐹)𝑦)))) | 
| 13 |  | simprl 770 | . . . . 5
⊢ ((𝜑 ∧ (𝑥 = 𝑋 ∧ 𝑦 = 𝑌)) → 𝑥 = 𝑋) | 
| 14 | 13 | fveq2d 6909 | . . . 4
⊢ ((𝜑 ∧ (𝑥 = 𝑋 ∧ 𝑦 = 𝑌)) → ((1st ‘𝐹)‘𝑥) = ((1st ‘𝐹)‘𝑋)) | 
| 15 |  | simprr 772 | . . . . 5
⊢ ((𝜑 ∧ (𝑥 = 𝑋 ∧ 𝑦 = 𝑌)) → 𝑦 = 𝑌) | 
| 16 | 15 | fveq2d 6909 | . . . 4
⊢ ((𝜑 ∧ (𝑥 = 𝑋 ∧ 𝑦 = 𝑌)) → ((1st ‘𝐹)‘𝑦) = ((1st ‘𝐹)‘𝑌)) | 
| 17 | 14, 16 | oveq12d 7450 | . . 3
⊢ ((𝜑 ∧ (𝑥 = 𝑋 ∧ 𝑦 = 𝑌)) → (((1st ‘𝐹)‘𝑥)(2nd ‘𝐺)((1st ‘𝐹)‘𝑦)) = (((1st ‘𝐹)‘𝑋)(2nd ‘𝐺)((1st ‘𝐹)‘𝑌))) | 
| 18 | 13, 15 | oveq12d 7450 | . . 3
⊢ ((𝜑 ∧ (𝑥 = 𝑋 ∧ 𝑦 = 𝑌)) → (𝑥(2nd ‘𝐹)𝑦) = (𝑋(2nd ‘𝐹)𝑌)) | 
| 19 | 17, 18 | coeq12d 5874 | . 2
⊢ ((𝜑 ∧ (𝑥 = 𝑋 ∧ 𝑦 = 𝑌)) → ((((1st ‘𝐹)‘𝑥)(2nd ‘𝐺)((1st ‘𝐹)‘𝑦)) ∘ (𝑥(2nd ‘𝐹)𝑦)) = ((((1st ‘𝐹)‘𝑋)(2nd ‘𝐺)((1st ‘𝐹)‘𝑌)) ∘ (𝑋(2nd ‘𝐹)𝑌))) | 
| 20 |  | cofu2nd.x | . 2
⊢ (𝜑 → 𝑋 ∈ 𝐵) | 
| 21 |  | cofu2nd.y | . 2
⊢ (𝜑 → 𝑌 ∈ 𝐵) | 
| 22 |  | ovex 7465 | . . . 4
⊢
(((1st ‘𝐹)‘𝑋)(2nd ‘𝐺)((1st ‘𝐹)‘𝑌)) ∈ V | 
| 23 |  | ovex 7465 | . . . 4
⊢ (𝑋(2nd ‘𝐹)𝑌) ∈ V | 
| 24 | 22, 23 | coex 7953 | . . 3
⊢
((((1st ‘𝐹)‘𝑋)(2nd ‘𝐺)((1st ‘𝐹)‘𝑌)) ∘ (𝑋(2nd ‘𝐹)𝑌)) ∈ V | 
| 25 | 24 | a1i 11 | . 2
⊢ (𝜑 → ((((1st
‘𝐹)‘𝑋)(2nd ‘𝐺)((1st ‘𝐹)‘𝑌)) ∘ (𝑋(2nd ‘𝐹)𝑌)) ∈ V) | 
| 26 | 12, 19, 20, 21, 25 | ovmpod 7586 | 1
⊢ (𝜑 → (𝑋(2nd ‘(𝐺 ∘func 𝐹))𝑌) = ((((1st ‘𝐹)‘𝑋)(2nd ‘𝐺)((1st ‘𝐹)‘𝑌)) ∘ (𝑋(2nd ‘𝐹)𝑌))) |